The Wisconsin Diabetes Registry Study (WDRS) is following one of very few population-based cohorts with type 1 diabetes in the United States. The cohort is unique in being comprehensively described from the time of diagnosis during 1987-1992 until now, with respect to glycemic control, diabetes care and complications. Hence, the WDRS is well situated to: (1) Determine how population wide changes toward more intensive insulin therapy and diabetes management have affected microvascular outcomes. (2) Investigate how glycemic control, diabetes care, insulin resistance and other factors across adolescence develop and affect later outcomes. These goals will be achieved by extending the observations through the twentieth year of type 1 diabetes, a duration over which an increase in microvascular complications is expected to occur Collaboration with the Wisconsin Epidemiologic Study of Diabetic Retinopathy (WESDR), makes it possible to directly examine the potential decline in complications in the context of suspected improvements in diabetes care in the same geographic region overtime in individuals diagnosed 7-10 years apart. Participation in the WSDR cohort is excellent. Standardized protocols for examinations, including fundus photographs and interviews, have been implemented throughout follow-up and will be used during this additional period of data collection. Clinical examinations will establish accurate prognostic information for the incidence, prevalence, and progression of retinopathy, kidney dysfunction and hypertension at 18-20 years duration of type 1 diabetes. Extensive longitudinal data and an existing plasma bank will be used to examine the effects of diabetes management, insulin resistance, body composition, markers of cardiovascular risk and indicators of kidney damage across and past the critical adolescent years. Patterns in these indicators will be investigated as predictors of outcomes. Specifically, cystatin C will be used as a longitudinal measure of kidney function and cardiovascular risk, and IGF-1 and adiponectin will be used to examine the development and role of insulin sensitivity across adolescence. The importance of insulin sensitivity in type 1 diabetes has recently been realized, but its development has not been comprehensively studied. Findings on the predictive role of plasma lipids, body composition, insulin therapy and insulin resistance during adolescence could have important implications for prevention of diabetes complications.